Production of sized alkaline paper



PRODUCTION OF SIZED ALKALINE PAPER Walter F. Reynolds, Jr., Stamford,Conn., assignor to American Cyanamid Company, New York, N. Y., acorporation of Maine No Drawing. Application April 18, 1951, Serial No.221,724

11 Claims. (Cl. 92--3) This invention relates to the production of sizedpaper by applying to the fibers thereof a novel class of SlZlIlg agentscharacterized by their high sizing efficiency and their ability to makesized paper under neutral and alkaline conditions. The inventionincludes the application of the novel sizing agents to paper, either inthe presence or absence of alkaline fillers, as well as the novel paperssized therewith, as will hereinafter be more fully described.

The manufacture of a sized alkaline paper has heretofore presented adefinite problem. Ordinary sizes, such as rosin size precipitated on thepaper fibers by alum, cannot be applied in the presence of alkalies.Similarly alkaline fillers such as calcium carbonate-type fillers cannotbe successfully incorporated into aqueous suspensions of paper pulp towhich rosin size and alum have already been applied; when this isattempted the s1z1ng action of the rosin size is lost. The principaldifficulty arises from the fact that such alkaline fillers impart arelatively high pH to the paper pulp suspensions, on the order of 9.0,whereas rosin sizing is carried out at pH values between and 6. Similardifiiculties are encountered when papers are made alkaline which containordinary wax sizes precipitated on the paper pulp by the use of alum. Aserious problem in sizing paper containing carbonate fillers is theformation of foam and bubbles when the stock is treated with alum todevelop the sizing properties.

The present invention is based on the concept of applying to aqueouspaper pulp suspensions a class of compounds containing a long chainaliphatic radical having a sufiiciently great chain length to impart thenecessary water resistance and ink resistance to cellulosic paper fiberssized therewith, these compounds being higher aliphatic amines condensedwith epichlorhydrin in such a manner that the condensation products arewatersoluble or water-dispersible but substantive to cellulosic paperfibers in dilute aqueous suspension. In the practice of the presentinvention aliphatic monoamines having hydrocarbon chain lengths of 16 ormore carbon atoms are reacted with epichlorhydrin in a quantitysufficient to form products containing from 1 to 2 mols ofepichlorhydrin condensed with each mol of amine.

In practicing the process of my invention a watersoluble orwater-dispersible higher aliphatic amineepichlorhydrin condensationproduct of the class described is added to a dilute aqueous suspensionof cellulosic papermaking fibers in quantities of from about 0.1 to 3-5%by weight under neutral or preferably under acid conditions. After thecondensation product has been absorbed by the cellosic fibers the stocksuspension is made alkaline, as by the addition of an alkaline fillersuch as finely divided calcium carbonate, aqueous sodium silicate or thelike. The stock is then made into paper by any suitable formingprocedure, as on a Fourdrinier machine or on a cylinder machine, and thepaper is heated in the usual manner to remove excess moisture. Duringthis heating, which is usually carried out by passing the paper over orbetween steam-heated drying rolls having temperatures between 200 F. and300 F. for a time of about 0.5-3 minutes, the sizing properties of thecondensation product are developed on the fibers and a well-sized paperis obtained.

My invention presents a number of important advantages both in sized butunfilled paper and in the production of sized paper containing-alkalinefillers. Sized papers that are neutral or alkaline in character, instead"rates Patent 0 understood that either alkyl amines (r. e., amines of ofacid, serve a number of important purposes. Thus, bag stock made fromkraft fibers develops its greatest mechanical strength under alkalineconditions; this is particularly important in the manufacture ofmulti-wall paper bags. Sulfite pulp and other pulps are frequentlybleached with alkaline bleaching agents, and a paper capable ofretaining its water-resistance, ink-resistance, and other properties ofa sized paper, after bleaching with alkaline bleaching agents, is ofconsiderable value. The sizing agents of the present invention areparticularly well adapted for use in processes wherein the paper isbleached on the papermaking machine, or immediately thereafter, andprior to the complete drying thereof. Papers sized in accordance withthe present invention are also well suited for impregnation withcommercial sodium silicate solutions, as for example by calender sizing,to provide better strength, printability and grease or oil resistance.Sodium silicate is also used as an adhesive in making boxboard.

Among the alkaline fillers for paper, finely divided calcium carbonateis by far the most widely used. However, other fillers such as Raifold(calcium carbonatemagnesium hydroxide), calcium sulfite, etc. areapplied to aqueous paper pulp suspensions under alkaline conditions andpresent much the same problem. These fillers are usually applied inquantities ranging from 550% up to or more of the dry weight of thepaper fibers in order to obtain paper containing from 2% to 30% of itsweight of filler. It is another important advantage of the process of myinvention that the aliphatic amineepichlorhydrin condensation productsenhance the retention of finely divided alkaline fillers by the paperpulp while, in turn, the water resistance and ink resistance imparted tothe fibers by the condensation product are not materially decreased bythe filler content of the sheet.

Papermaking fibers impregnated or coated with from 0.1% to 1.5% or moreof the higher aliphatic amineepichlorhydrin condensation products canalso be further sized with wax sizes, with starch or other amylaceoussizing agents, or with proteins or gums in amounts of from 0.1% to 3% ormore prior to forming them into paper. It should be noted, however, thatrosin sizes or other forms of abietic acid should not be used along withthe condensation products, as they appear to destroy the sizing action.For this reason wax sizes contaimng rosin soaps as emulsifying agentsshould not be employed, although other soap-type wax emulsions aresuitable.

The higher aliphatic amine-epichlorhydrin condensation products used inpracticing the invention are obtained by heating either an aliphaticamine or a salt thereof with a quantity of epichlorhydrin sufficient toform a condensation product containing from 1 to 2 mols of combinedepichlorhydrin for each mol of aliphatic amine. When epichlorhydrin anda free higher aliphatic amine are used the proper proportion of reagentsto be mixed together is from equimolecular quantities up to slightlymore than 2 mols of epichlorhydrin for each mol of amine. When aminesalts are used the molar ratio of epichlorhydrin can be considerablyhigher, extending up to about 3:1. This difference appears to resultfrom the fact that the amine salts do not react with epichlorhydrin asreadily or as completely as do the free amines themselves; therefore, alarger proportion of epichlorhydrin may be used. The fact appears to bethat no more than 2 mols of epichlorhydrin can be reacted with 1 mol ofa higher aliphatic monoamine such as octadecylamine, regardless of theexcess of epichlorhydrin in the reaction mixture; the unreactedepichlorhydrin appears to form glycerol dichlorohydrin that does notfunction as a sizing agent.

In general, therefore, the condensation products suitable for use inpracticing the invention are those containing from 1 to 2 mols ofepichlorhydrin condensed with 1 mol of higher aliphatic amine or aminemixture having an average molecular weight corresponding to ahydrocarbon chain length of from 16 to 22 carbon atoms. The preferredaliphatic monoamines used are those of about 16-18 carbon atoms, sincethese are obtainable commercially at reasonably low cost. It will besaturated character) or alkenylamines (unsaturated amines) may beemployed; however, it is preferred that at least 50% of the aminehydrocarbon be fully saturated.

In preparing the condensation products the amine is preferably dissolvedin a solvent such as ethanol, pro panol, butanol or the like, and theepichlorhydrin is added slowly at temperatures below about 90 C. Afterall the epichlorhydrin has been added the solution is heated until awater-soluble or water-dispersible condensation product is formed. Thesolvent can then be removed by distillation at reduced pressure and thesizing agent obtained as a waxy material. In carrying out thecondensation, care should be taken to use relatively mild reactionconditions, such as temperatures not substantially higher than 100 C.,and to stop the reaction when an initial condensation product has beenformed. If the reaction is carried out for too long a time, or ifexcessively high temperatures are used, there is danger of forming apolymerized condensation product that has greatly reduced efliciency asa sizing agent and that is not readily dispersed in water.

The quantity of condensation product to be employed depends on the typeof paper pulp used, on the water resistance and ink resistance desired,and on the heating times and temperatures to be employed in drying thepaper. I find that as little as 0.2% to 1% can be employed, based on thedry weight of the paper pulp, when the paper is dried by contact withdrying rolls heated to 130150 C. for 1 minute, or at 115l30 C. for 2minutes. Larger quantities of the sizing agent, within the range of 1-2%on the dry weight of the paper pulp, will produce good results whenheating times and temperatures of 115-130 C. for 0.5-1.5 minutes areemployed. Still larger quantities of sizing agents, up to 3% or inextreme cases up to 5%, may be used; however, amounts of more than 3%are seldom advisable. When wax sizes, starches, gums or other materialsare employed, they are usually used in quantities of from 0.1% to 0.5 upto about 1% based on the dry weight of the paper. Ordinarily, theoptimum quantities of such mixed sizing agents are about 0.5% to 1% ofthe condensation product along with 0.1% to 0.5% of the wax size orother auxiliary size, based on the weight tion product. Starches, gumsand hydrocarbon wax sizes may also be added.

The invention will be further described by the following specificexamples. It should be understood, however, that although these examplesmay describe certain features of the invention in detail, they are givenprimarily for purposes of illustration and the invention in its broaderaspects is not limited thereto.

Example I A solution of 103.7 grams (0.371 mol) of Armeen D, acommercial octadecylamine having a molecular weight of 279,5, in 150 cc.of ethanol was converted into the hydrochloride by adding 13.7 grams(0.371 mol) of concentrated hydrochloric acid. The solution was heatedto 70 C. and 68.6 grams (0.742 mol) of epichlorhydrin was added withcooling at the rate of about 5-8 cc. per minute while maintaining thetemperature below 70 C. The mixture was then boiled under a refluxcondenser for 4 hours, the solvent removed by distillation and theproduct was stripped under a partial vacuum. The residue was an opaque,dark brown soft wax containing 1.3 mols of combined epichlorhydrin foreach mol of amine.

This product was tested as a sizing agent in calcium carbonate-filledpaper by the following procedure. A beaten stock composed of sulfite andsoda pulp was diluted with demineralized water to 0.6% consistency andseparated into a number of portions. To these the higher aliphaticamine-epichlorhydrin condensation product was added. Corn starch and waxsize were also added to some of the portions. In the table below thepercentages of these sizes are based on the dry weight of the fibers.

A quantity of finely divided calcium carbonate filler equal to the dryweight of the paper fibers was then added and the stock having a pH of9.0 was made into paper on a Nash laboratory handsheet machine. Thehandsheets were couched onto blotting paper and dried at the temperatureand during the times shown in the table below. The dried sheets wereanalyzed for calcium carbonate content and tested for sizing (waterresistance) by the Currier size tester (slack scale) and for inkresistance on the B. K. Y. tester. The test results, expressed inseconds, are shown in the following table:

Dried 1 min. at Dried 2 min. at 130 0. 130 C.

Drying Temperature 150 C. for 1 Min.

of the paper.

From the foregoing it will be seen that my invention consists in theproduction of paper having the novel characteristic of retaining underalkaline conditions its water resistance, ink resistance and otherproperties of a sized sheet. This is accomplished by impregnating thecellulosic paper fibers, while in dilute aqueous suspension, with asmall quantity of the condensation product of from 1 to 2 mols ofepichlorhydrin with 1 mol of an aliphatic amine containing at least 16carbon atoms, forming the treated fibers into paper or other similarwaterlaid product, and heating the paper while the pH of the stock is 7or higher, and preferably 7.510.0, at'temperatures of 100150 C. orhigher and for a time sufficient to dry the paper and develop the sizingproperties of the condensation product thereon. The paper stock may alsobe impregnated with an alkaline sizing material, such as calciumcarbonate, prior to the forming step without interfering with the sizingproperties of the condensa- Example 2 A solution of 496 grams (1.84mols) of octadecylamine in 700 cc. of ethanol was neutralized by adding155 cc. (1.84 mols) of concentrated hydrochloric acid. It was thenheated to 65 C. and 511 grams (5.52 mols) of epichlorhydrin was addedduring a 50 minute period at the rate of 5-8 cc. per minute. During thisaddition the reaction mixture was cooled to a maximum temperature of 74C. Fifteen minutes after the addition was complete the solution washeated to boiling and refluxed 4 hours. After removing volatiles thecondensation product was obtained as a light brown clear syrup whichcooled to a soft tan paste.

This product was added to samples of an aqueous paper pulp suspensionwhich were then sized by adding of calcium carbonate and made intohandsheets. These handsheets were driedand tested in the usual mannerwith the following results:

ae s-gees A. A condensation product was prepared from octadecylamine andepichlorhydrin in the molar ratio of 121.2. This was done by dissolving146 grams (0.5 mol) of a commercial octadecylamine in 125 cc. ofalcohol, heating to 65 C. and adding 55.5 grams (0.6 mol) ofepichlorhydrin during minutes, followed by boiling the mixture under arei'lux condenser/for 4 hours. The solvent was distilled and the residuestripped of volatiles by heatin at reduced pressure, whereupon the solidcondensation product was obtained as a light tan colored wax.

B. A similar condensation product was prepared by adding theepichlorhydrin to the octadecylamine solution in the molar ratio of1.4:1. A solution of 146 grams of octadecylamine in 125 cc. of alcoholWas used and 64.8 grams (0.7 mol) of epichlorhydrin was added duringminutes. The mixture was then refluxed 4 hours and stripped of solventsin the usual manner.

C. Following the same procedure, 146 grams (0.5 mol) of commercialoctadecylamine was reacted with 83.2 grams (0.9 mol) of epichlorhydrinto form a condensation product.

1). A solution containing 146 grams (0.5 mol) of commercialoctadecylamine in 150 cc. of ethanol was prepared and heated to 65 C. Tothis solution 92.5 grams (1 mol) of epichlorhydrin was added uniformlyduring 12 minutes, the temperature being maintained below 75 C. Theresulting mixture was boiled 4 hours under a reflux condenser, thesolvents removed by distillation at reduced pressure and the residuestripped of volatiles in the usual manner. There was obtained 223.2grams of octadecvlam...e-epichlorhydrin condensation product as a light,brittle, tan colored Wax.

E. A solution of 292 grams (1 mol) of commercial octadecylamine in 300cc. of ethanol was prepared and 232 grams (2.5 mols) of epichlorhydrinwere added over a 48 minute period. The mixture was refluxed 4 hours andstripped of solvent and volatiles in the usual manner.

These condensation products were dissolved in water and added to aqueouspaper pulp suspensions in amounts of 1%, based on the dry weight of thefiber. A quantity of calcium carbonate filler equal to the dry fiberweight was then added and handsheets were made and tested, the procedurebeing the same as that described in Example 1. The test results were asfollows:

Dried l min. at Dried 2 min. at Percent 130 C. 130 C. Prepn. EpizAmineC2003 in Sheet Currie B. K. Y. Currie B. K. Y.

These results show that condensation products of from 1 to 2 mols ofepichlorhydrin with 1 mol of a higher aliphatic amine are good sizingagents for paper. It will be noted from Example 2 that. good sizingagents can also be prepared using higher molecular ratios of aliphaticamine salts.

Example 4 A furnish consisting of'60-% bleached sulfite' and 40%bleached.- soda pulp was suspended in water, beaten to a Green freenessof'475 and divided into portions. To these there was added 1.5% of theabove-described condensation :product. The pH was then adjusted to720 orto 9.0 by adding aqueous sodium hydroxide after which the consistencywas adjustedto 0.6%by adding'bufiered demineralized water. The stock soprepared was made into handsheets on a Nash laboratory handsheet machineand the. sheets were dried for l'minute at 130 C. on a laboratory drumdryer. Tests for water and ink resistance were then made with thefollowing results:

, Currier pH (slack) B. K. Y.

Example 5 A beaten unbleached kraft pulp was diluted with water to 0.6%consistency and portions were treated with the condensation product ofExample 3-3 in amounts varying from 0.25 to 1.5 based'on the dry weightof the fiber While. other'portions remained untreated. In all 'cases asulficient quantity of sodium hydroxide solution was then added, afterfirst adding the octadecylamineepicllorhydrin condensation product, toraise the pH to 9.

The treated and untreated pulps were made into handsheets on a Nashlaboratory handsheet machine. The handsheets were couched onto blottingpaper, pressed between wool felts in a laboratory rotary press and driedon a drum dryer for 1 minute at 115 C. Handsheets were tested for Waterresistance by the Currier size tester (hard scale) and for. inkresistance by the B. K. Y. tester. The results are given in thefollowing table wherein the figures mean seconds of time'requiredtopenetrate the paper except where otherwise indicated.

Water Resistance Ink Resistance Percent Sizing Agent Example 6Handsheets were made by the usual procedure from a beaten 100%unbleached sulfite pulp treated at 0.6% consistency with 1.5 based onthe dry fiber weight, of the condensation product of Example 3B and madealkaline to a pH of 9.0 by adding NaOH solution. The 1181;?211685 weredried on a heated drum for 4 minutes at Portions of these handsheetswere subjected to peroxide bleaching by impregnating the sheets with analkaline aqueous peroxide bleaching solution containing 0.5 hydrogenperoxide and 0.75% trisodium phosphate. A 6% pickup of bleachingsolution was realized. The impregnated sheets were dried on a heateddrum at C. for 2 minutes. The brightness (per cent reflectance at 454rnillimicrons) and water resistance were determined for the bleached andunbleached sheets. The Currier size tester (hard scale) was employed forthe water resistance sizbe1 test. The test results are shown in thefollowing ta e:

Under similar circumstances, a rosin sized sheet would lose practicallyall its water resistance on being subjected to an alkaline bleachingsolution.

What I claim is:

1. A method of producing paper sized by an absorbed content of anepichlorohydrin-amine condensation product which comprises preparing adilute aqueous suspension of cellulosic papermaking fibers, addingthereto a small quantity of a water-soluble initial condensation productof from 1 to 2 mols of epichlorhydrin with 1 mol of an aliphatic aminecontaining at least 16 carbon atoms, whereby said condensation productis absorbed by said fibers, forming the treated fibers into paper, andheating the paper at a pH higher than 7.0 to dry the same and developthe sizing properties of the condensation product thereon.

2. A method according to claim 1 in which the condensation product isformed by condensing from 1 to 3 mols of epichlorhydrin with 1 mol ofaliphatic primary amine of from 16 to 22 carbon atoms.

3. A method according to claim 1 in which the quantity of condensationproduct added to the papermaking fibers is within the range of from 0.2%to 5% 4. A method of producing paper sized by an absorbed content of anepichlorohydrin-amine condensation product containing an alkaline fillerwhich comprises preparing a dilute aqueous suspension of collulosicpapermaking fibers, adding therto a small quantity of a water-solubleinitial condensation product of from 1 to 2 mols of epichlorhydrin with1 mol of an aliphatic amine containing at least 16 carbon atoms, wherebysaid condensation product is absorbed by said fibers, mixing a finelydivided alkaline filler with the suspension of fibers so treated,forming the resulting furnish into paper and heating the paper at a pHhigher than 7 to dry the same and develop the sizing properties of thecondensation product thereon.

5. A method according to claim 4 in which the alkaline filler is calciumcarbonate.

6. A method according to claim 4 in which the quantity of condensationproduct added to the napermaking fibers is within the range of from 0.2%to 3 7. A method of producing paper sized by an absorbed content of anepichlorohydrin-amine condensation product and containing a member of.the group consisting of starches, gums and hydrocarbon waxes whichcomprises preparing a dilute aqueous suspension of cellulosic papermaking fibers, adding thereto a small quantity of a watersoluble initialcondensation product of from 1 to 2 mols of epichlorhydrin with 1 mol ofan aliphatic amine containing from 16 to 22 carbon atoms, whereby saidcondensation product is absorbed by said fibers, adding to the fibers sotreated a quantity of an aqueous dispersion of a member of the groupconsisting of starches, gums and hydrocarbon waxes sufficient to depositabout 0.1% to 3% of the dry fiber weight thereon, forming the resultingfurnish into paper and heating the paper at a pH higher than 7 to drythe same and develop the sizing properties of the condensation productthereon.

8. A method according to claim 7 in which the quantity of condensationproduct added to the cellulosic fibers is within the range of from 0.1%to 1.5%.

9. Paper composed of felted cellulosic fibers sized by an absorbedcontent of about 0.1% to 5% of their dry weight of a water-solubleinitial condensation product of from 1 to 2 mols of epichlorhydrin with1 mol of an aliphatic amine containing from 16 to 22 carbon atoms andheated at about 100150 C. for about 0.5 to 3 minutes to develop thesizing properties thereof.

10. Paper as defined in claim 9 carrying about 5-30% of an alkalinefiller.

11. Paper as defined in claim 10 in which the alkaline filler is acalcium carbonate filler.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,970,578 Schoeller et al Aug. 21, 1934 2,040,878 Rafton May19, 1938 2,469,683 Dudley et al. May 10, I949 2,492,702 Neubert et al.Dec. 27, 1949 2,520,093 Gross Aug. 22, 1950 2,601,598 Daniel et al June24, 1952

9. PAPER COMPOSED OF FELTED CELLULOSIC FIBERS SIZED BY AN OBSORBEDCONTENT OF ABOUT 0.1% TO 5% OF THEIR DRY WEIGHT OF A WATER-SOLUBLEINITIAL CONDENSATION PRODUCT OF FROM 1 TO 2 MOLS OF EPICHLORHYDRIN WITH1 MOL OF AN ALIPHATIC AMINE CONTAINING FROM 16 TO 22 CARBON ATOMS ANDHEATED AT ABOUT 100-150* C. FOR ABOUT 0.5 TO 3 MINUTES TO DEVELOP THESIZING PROPERTIES THEREOF.